The Return would be the second best, Into the Shit.
S/T is average Venom and early thrash worship. He really found his own voice with The Return. AND I WILL FIGHT ANYONE WHO DISAGREES. Well not really, but that's my opinion.

After all those years ,I'll go with ''Under the sign....''.
All of them are masterpieces and classics ,the one different from other.
The only bands who can be compared with those milestones are early Celtic Frost and Mayhem's DMDS.

Mmm,Sodom was more about the noisy and chaotic sound for me (ep and ''Obsessed..'',and Venom's message was more rock n roll and fun.
Celtic frost and Bathory are way more ''serious'' on satanic thematology and the feeling of darkness.
To megatherion album might be the darkest album ever?Along with Under.. and DMDS